1. Field of the Invention
This invention relates generally to the fields of molecular biology and medicine and more specifically to a protein that is active primarily in malignant tumor tissue but not in non-cancerous tissue, the protein activity being diagnostic of cancer in a subject.
2. Background Information
Cancer is the second most common cause of death in the United States. Breast cancer, for example, is diagnosed in more than 180,000 women in the United States each year. In most cases, the cancer is not detected until it becomes palpable. However, the prognosis is not good for a patient presenting with a palpable breast tumor. Due, in part, to the late detection of breast tumors, approximately one-third of the women diagnosed with breast cancer will die from the disease.
In order to detect breast cancer at an early stage, women that are 50 years of age or older and women that have a family history of breast cancer are encouraged to have yearly mammograms. Unfortunately, mammography cannot definitively confirm whether a breast tumor, particularly a small tumor, is malignant. Furthermore, mammography suffers from the limitation that it does not provide any information as to the type or stage of a breast cancer and cannot indicate whether an apparently benign tumor contains malignant tumor cells. Thus, mammography provides little if any prospective information as to the prognosis of a patient.
Currently, lymph node status provides the most reliable information as to the prognosis of a breast cancer patient. However, this method is not perfect, as about 20-30% of patients that have negative axillary lymph nodes will experience recurrence of the disease.
Significant research has been directed to identifying cancer-associated tumor markers. The recent association of breast cancer with the gene, brca-1 ("breast cancer-1"), was hailed as a break-through for identifying women at high risk of developing breast cancer. However, brca-1 is a very large gene that shows a significant degree of polymorphism in the human population. These characteristics of brca-1 will make the development of a screening assay much more complicated than initially hoped. In addition, brca-1 only is useful for identifying a subpopulation of breast cancers and likely will provide limited if any utility in predicting the prognosis of the disease.
Histologic examination of a biopsy sample of the tumor can provide more definitive information as to the type and stage of a tumor and, therefore, as to the prognosis of the patient. However, histologic examination suffers from the subjective nature of the method. Thus, a need exists to identify a cancer-associated tumor marker that is diagnostic of cancer and prognostic as to the course of the disease. The present invention satisfies this need and provides related advantages as well.